• Laying hens affected by Blackhead were able to increase egg production above the breed standard by >5% following the inclusion of Orego-Stim (600g/t followed by 300g/t) in their feed.
  • Egg production of laying hens on the same unit, but apparently unaffected by Blackhead, was also shown to increase 5% above the breed standard following the inclusion of Orego-Stim (300g/t) in the feed.


  • Blackhead in laying hens can result in mortality and poor laying performance and is a result of infection by the parasite Histomonas meleagridis.
  • Natural products such as those based on oregano have anecdotally been indicated to help manage histomoniasis outbreaks.



The Histomonas outbreak occurred in one section of a free-range laying farm in the UK, comprising two houses (1 and 2) containing approximately 16,000 Lohman hens each. Laying in both houses commenced at 20 weeks. Orego-Stim (OS) was introduced in the feed at 600g/t for 4 weeks in week 32. At week 37 OS inclusion was reduced to 300g/t. Egg production (EP) and mortality were monitored throughout.


House 1:

Histomoniasis was diagnosed as the cause of the sharp increase in mortality at 25 weeks. At week 31, prior to OS inclusion, EP was below breed standards. After the first OS inclusion, EP was 95.2% and at week 48, EP recovered to be 5.8% higher than the breed standard. Average daily mortality over the recorded production period was 0.015%.

 House 2:

No incidence of Blackhead was recorded and average daily mortality over the 32 week period was 0.004%. OS was included in the feed from week 33 onwards at 300g/t. By week 32, EP was 92.9%. EP in house 2 peaked in week 36 (94.4%) and by week 48, EP was 93.8% which is 4.8% above the breed standard.

  • Egg production in both the Blackhead affected and healthy houses increased following the inclusion of OS in the feed and remained higher than the breed standard from week 32 onwards.
  • This trial has shown that Orego-Stim can help to restore, and maximise, laying performance following a Blackhead outbreak.